Oven for heating electric lamp envelopes



June 10, 1958 s. c. SHAPPELL OVEN FOR HEATING ELECTRIC LAMP ENVELOPES 2 Sheets-Sheet 1 Original Filed Oct. 31, 1955 NVENTOR TANLEYC. BY c ATTORN SHAPZELL June 1958 s. c. SHAPPELL OVEN FOR HEATING ELECTRIC LAMP ENVELOPES 2 Shee ts-Sheet 2 Original Filed Oct. 31, 1955 INVENTOR STANLEY C JWAPPELL ATTORNEY United States Patent C) OVEN FOR HEATING ELECTRIC LAMP ENVELOPES Stanley C. Shappell, West Boxford, Mass., assignor to Sylvania Electric Products Inc., Salem, Mass., a corporation of Massachusetts 3 Claims. (Cl. 263-8) This invention relates to the manufacture of electric lamps, and more particularly to apparatus for heating lamp envelopes during the manufacturing process.

In the manufacture of electric lamps, such as fluorescent lamps for example, the lamp envelope is usually heated one or more times during the manufacturing operations. For example, the lamp envelope is usually heated to a temperature sufiicient to decompose the binder employed in the application of a suspension of luminescent material to the inner wall of the lamp envelope. In a subsequent operation, the lamp envelope is connected to an exhaust system to effect evacuation of impurities therefrom, Since exhausting ofthe lamp envelope can be performed more satisfactorily and more efiiciently if the lamp envelope is hot, heat is usually applied to the lamp envelope during the exhausting operation or, as taught in my copending application, Serial No. 543,673, filed October 31, 1955, now Patent No. 2,789,587, immediately before the start of this operation. 7

At the present time many types of fluorescent lamps are manufactured. The length-of these lamps vary considerably. Forcxample, some are two feet long, others are four feet long, and some are eight feet in length. Heating of the lamp tubes is usually effected in an oven through which the lamp tubes are caused to pass. Because of the great difference in the lengths of the lamps manufactured, either a separate oven foreach length 'of lamp must be used or an oven large enough to accommodate several different lamp lengths must be employed. In the former case, a large capital investment and considerable floor space is required; in the latter case operating efiiciency of the oven is very low when relatively short lamp tubes are heated in an oven much larger in .size than required for a particular lamp tube.

In view of the foregoing, an object of this invention is to heat lamp tubes efiiciently and economically.

Another object is to provide an oven for heating lamp tubes of various lengths efficiently and economically.

These and other objects, advantages and features are attained, in accordance with the principles of my invention, by disposing within an insulated enclosure, which defines the walls of an oven, a plurality of burner pipes extending substantially parallel to the longitudinal axis of the oven and transverse to the path through which the lamp tubes are caused to pass as they are moved through the oven. Each burner pipe is provided with a plurality of ports and each burner pipe is provided with its own controls. Thus, the number of burners which are fired is determined by the length of the lamp tubes to be heated. This arrangement insures eflicient operation of the oven because, when relatively short lamp tubes are to be heated, only those burners lying in the path to be traversed by the lamp tubes have to be ignited. Similarly, when relatively longer lamp tubes are to be heated, such additional burners as necessary may be ignited. The burner pipes are preferably substantially rectangular in cross-section and disposed beneath ice the work in order to insure a high degree of uniformity of heating.

In the specific embodiment of my invention illustrated in the accompanying drawing, Figure. 1 is a side elevational view, partly in section, of the oven; and Figure 2 is a plan view of the oven of Figure 1 with the roof thereof removed.

Referring now to the drawings, the oven frame, which is fabricated primarily from angle iron and channel iron stock, comprises a channel iron base 12 attached toangle iron legs 14 intermediate their ends. Angle iron side supports 16 are mounted on the upper ends oflegs 14. Bearing housings 18 and 20, mounted on side supports 16, support the oven conveyor drive shaft 22. Bearing housings 24 and 26, mounted on side supports 16, support the oven conveyor idler shaft 28. Idler shaft 28 is provided with a plurality of sprockets 30, and drive shaft 22 is provided with a plurality of sprockets 32. The several sprockets 30 are connected to the several sprockets 32 by chains 34, and the upper reaches of which ride on chain tracks 35 mounted on brackets 37. Each of the chains 34 is provided with a plurality of fingers 36' attached thereto and upstanding thereon. The oven conveyor drive shaft 22 is driven by some suitable means, such as the drive shaft of an associated machine for example, through chain 40, sprocket 42 .on shaft 44, sprocket 46 on shaft 44, and chain 48 which connects sprocket 46 to a sprocket 50 on the oven conveyor drive rality of burner ports 55. The burner pipes 54 are attached at two points intermediate their ends to support plates 56 mounted on top of posts 58 upstanding on channel iron bars 60 which are mounted on base members 62 attached to side supports 16. Since the burner sup- 7 port plates 56 lie in substantially the same horizontal plane as the upper reaches of the chains 34, separate plates 56 are used between the upper reaches of the chains 34 in order to provide a free path therefor. Further support of the burner pipes 54 is effected by anchors 64 which connect each of the burner pipes 54 to a tube 66 mounted in brackets 68 attached to side supports 16. The roof 70 of the oven, which comprises a plurality of sheets of stainless steel, is supported from the channel iron base 12 by channel iron legs 72 and channel iron cross bars 74.

Lamp tubes may be fed to the oven manually or by a suitable feeding mechanism. In either case, a lamp tube is disposed initially in the position occupied by lamp tube 1a on the right side of Figure 1, i. e., resting on discs 76 mounted on idler shaft 28 and supported by fingers 36a on chains 34. As the chains 34 advance the lamp tube 1a into the oven, the lamp tube it: rolls off of the discs 76 and onto rods 78. The rods 78 are mounted on brackets 80 which are attached to channel iron bars 60. Due to the inclination of the rods 78, the lamp tube 1a rolls away from fingers 36a and into engagement with the fingers immediately forward thereof, assuming the position occupied by lamp tube 1b (Fig. 1) in engagement with fingers 361'). In order to define a free path for the fingers 36 as they enter the space between the burner pipes 54 and to protect the burner pipes therefrom, plates 82 (Fig. 2) are mounted on the burner pipes 54 to guide the fingers 36 into the spaces between the burner pipes.

As the lamp tubes advance through the oven they are heated by the burners, to which a combustible mixture is supplied by manifold 84 through tubing 86. As the lamp tubes approach the exit of the oven they move into engagement with the periphery of discs 88 attached to shaft 22.' When the lamp tubes move. off of the rods 78, they are supported by the discs 88 and carried by the fingers 36' until they are removed therefrom by some suitable means, such asmember 10 for example.

The oven is designed particularly for use in conjunction with an exhaust machine of the type shown in my co-pending application, Serial No. 543,673, filed October 31, 1955, i. e., an exhaust machine in which the heads to which one end of the lamp tubes are connected are adjustable longitudinally with respect to the heads to which the other end of the lamp tubes are connected in order to accommodate lamp tubes of different lengths. Thus the burner pipes 54 are disposed in a plane substantially perpendicular to. the plane in which the longitudinal axis of the lamp tube is disposed as it moves through the oven. Since each burner pipe 54 is provided with its own tubing 86 connecting it to the manifold, individual valves 87 are provided to permit regulation of the flow of gas to each burner pipe 54. This arrangement insures eflicient operation of the oven because, when relatively short lamp tubes are to be heated, only those burners lying in the path to be traversed by the lamp tubes have to be ignited. Similarly, when relatively longer lamp tubes are to be heated, such additional burners as necessary may be ignited.

This application is a division of my co-pcnding application Serial No. 543,673, filed October 31, 1955, now Patent No. 2,789,587.

What I claim is:

1. An oven for heating elongated tubular electric lamp envelopes comprising: an insulated enclosure having an opening at each end thereof defining an entrance and an exit; a conveyor, inclined from said entrance to said exit, for carrying elongated tubular electric lamp envelopes through said insulated enclosure from said entrance to said exit, with the longitudinal axes of said envelopes transverse to the longitudinal axis of said enclosure; and heating means disposed beneath the path traversed by said lamp envelopes moving through said enclosure and substantially parallel to the longitudinal axis of said enclosure.

2. An oven for heating elongated tubular electric lamp envelopes comprising: an insulated enclosure having an opening at each end thereof defining an entrance and an exit; a conveyor, inclined from said entrance to said exit, for carrying elongated tubular electric lamp envelopes through said insulated enclosure from said entrance to said exit, with the longitudinal axes of said envelopes transverse to the longitudinal axis of said enclosure; heating means disposed beneath the path traversed by said lamp envelopes moving through said enclosure and sub stantially parallel to the longitudinal axis of said enclosure, said heating means comprising a plurality of closely spaced burner pipes, each having a plurality of burner ports therein; and independent means for controlling the flow of a combustible gaseous mixture to each of said burner pipes.

3. An oven for heating elongated tubular electric lamp envelopes comprising: an insulated enclosure having an opening at each end thereof defining an entrance and an exit; a conveyor, inclined from said entrance to said exit, for carrying elongated tubular electric lamp envelopes through said insulated enclosure from said entrance to said exit, with the longitudinal axes of said envelopes transverse to the longitudinal axis of said enclosure; heating means disposed beneath the path traversed by said lamp envelopes moving through said enclosure and substantially parallel to the longitudinal axis of said enclosure, said heating means comprising a plurality of closely spaced burner pipes substantially rectangular in cross-section, each having a plurality of burner ports therein; and independent means for controlling the flow of a combustible gaseous mixture to each of said burner pipes.

References Cited in the file of this patent UNITED STATES PATENTS 1,903,878 Powers Apr. 18, 1933 2,139,067 Boax Dec. 6, 1938 2,391,970 I-Iolleran et al. Jan. 1, 1946 2,530,778 Otto Nov. 21, 1950 2,698,170 Foley Dec. 28, 1954 2,795,411 Court June 11, 1957 

